From: Phlip <phlip2005@...>
Date: 2008-09-09T19:58:40+09:00
Subject: Re: Why is Ruby dynamic?

David Masover wrote:

> A nitpick, but... string evals considered harmful!

>>        eval '

> I always loved define_method.

I recently tried define_method and it didn't work, so I fell back to eval. (Note 
to the newbs: Try things the most progressive way possible, such as a fixed 
version of Dave's version of my example, before trying a hack...)

Here's the lines, from inspect_sql:

   def self._decorate_explainers(explains) #:nodoc:
     def explains.find_statements(regexp)
       return AssertEfficientSql._decorate_explainers(select{|explanation|
         explanation[:statement] =~ regexp
       })
     end

     (_multiples + _singulars).each do |rollup, explainer|
       eval "def explains.#{rollup}; map{|q|q[:#{rollup}]}.flatten.uniq; end"
     end

     return explains
   end

For the eval line, I first tried explains.define_method, and it didn't work. 
Instead of researching why, or finding a kindler gentler system, I whipped out 
eval and put a bullet thru the problem.

It's the shortest possible eval, anyway!

Also I think you can't say 'def foo; def bar; end; end' - the def is in 
method-space, not class-space.

-- 
   Phlip